Lentis/Ecological Implications of Commercial Marine Fishing

From Wikibooks, open books for an open world
Jump to navigation Jump to search

Overview[edit | edit source]

Bycatch from commercial fishing

Trends in many marine populations today mirror those of previous mass extinction events. While most attention is focused on climate change, ocean warming, and ocean acidification, today, the greatest declines of life in the ocean are from overfishing[1]. It is predicted that there has been an 84% decline in large marine animals from historical baselines, including nearly a decline of 95% in sea turtles, 90% in coastal birds, and 70% in whales[2]. A number of coastal birds, the North Atlantic Right Whale, and all sea turtles species found in US waters are listed under the Endangered Species Act, one of the most popular bipartisan conservation laws. Overfishing and climate change will send our oceans past an ecological tipping point without intervention. This may include species extinctions and irreversible change of benthic (seafloor) habitats that critically support marine biodiversity.

Certain fishing methods, especially bottom trawling, are contributing to marine animal declines and making it harder for populations to recover due to habitat destruction[3]. Recovery of seafloor after trawling disturbances takes years; often, these areas never are able to fully recover before being fished again[4]. The combination of both direct and indirect human impact on marine ecosystems, especially benthic areas, is why management is becoming increasingly pertinent.

History[edit | edit source]

Rise of Overfishing[edit | edit source]

While the rise of overfishing is often attributed to have started around the mid-1900s, some will say that it can go back to the 1800s and possibly beyond that with commercialization attributed as a factor of more fishing over time[5]. Around 1870, 300,000 tons of herring was being caught every year which is about the same as the allowable yearly catch in modern times[5]. In the mid 1900s, more efficient and modern techniques began to develop through the evolution of technology and development of sophisticated methods[6]. Consumers became used to having access to a wide selection of fish products which created a cause for more fishing. Although, since 1989 when 90 million metric tons of catch was taken from the ocean, yields have stagnated as a result of overfishing[6]. According to the United Nations Food and Agriculture Organization (FAO), 34.2% of the fish stocks from the world’s fisheries had become overfished in 2017[7].

Fishery Subsidies[edit | edit source]

According the FAO, a fishery subsidies can be defined as "government actions or inactions that are specific to the fisheries industry and that modifies - by increasing or decreasing - the potential profits by the industry in the short-, medium- or long-term"[8]. Subsidies related to fishing can date back as far as the 1600s and throughout have been generally used to settle disputes related to fishing territories[9]. In the mid 1900s, the United States government began to help more in expanding the fish market which included allowing foreign access to fish in the waters of the United states in exchange for allowing more foreign market access to the United States[9]. Today, the estimated global costs of fisheries is $15 billion-$35 billion[10]. Rashid Sumaila and Daniel Pauly of the University of British Columbia found that over $150 million are paid to deep sea fisheries that would have losses of $50 million otherwise[11]. Much of this money is used for fuel in order to be able to do bottom trawling, a fishing technique that is very destructive[11]. The dangers of overfishing and threats to sustainability that subsidies provide has been met with protest. 300 scientists around the world have called on the World Trade Organization (WTO) to ban these harmful subsidiaries[12].

Methods of Commercial Fishing[edit | edit source]

There are many different methods which commercial fisheries use to catch fish. Different methods are more effective for certain fish species and environments than others. Similarly, certain methods are more conducive to large scale fishing operations while others are more accessible to smaller, individual fisheries.

Bottom Trawl[edit | edit source]

Bottom Trawling

Bottom Trawl, also called Otter Trawl, consists of a net being weighted so that it falls to the sea bed[13][14]. That net is then dragged across the bottom to collect the fish in its path. The speed at which the net is pulled prevents the fish which it catches from escaping. The size of the mesh in the net dictates which fish are caught and which can escape. The rationale behind this is that fish below a certain size provide no commercial benefit and thus can be let go. There are many variations of bottom trawling which differ in factors such as the type of net used or the number of boats pulling the net. A notable variation of the bottom trawl is called Pulse or Electrical Trawling. To conduct pulse trawling, an electric shock is sent through the trawl net which shocks the fish out of the seabed making them easier to catch.

Purse seine

Purse Seine[edit | edit source]

Purse seining is accomplished by locating a school of fish and wrapping a net around the school, preventing escape[13]. The net is then pulled together in the same fashion as a draw-string bag and dragged aboard the fishing boat with the fish inside. The biggest nets can be thousands of meters long, up to 250 meters deep and catch up to 400 tons of fish[14]. Frequently a speed boat is used to wrap the net around schools of fish of this scale.

Gill Net[edit | edit source]

The Gill Net is set up to effectively be a wall filled with holes[13][14]. Fish swim into the net and are caught by their gills, preventing escape. Some gill nets are fixed in a particular location, while others, referred to as Drift Nets, move with the tides and currents[15]. The tangle net functions similarly and catches fish which become tangled in the netting. The benefit to fisheries of gill nets and tangle nets is that they require much smaller motor boats, and are a more accessible fishing method for smaller scale or less developed fisheries.

Longline[edit | edit source]

Longlines are long fishing lines with closely spaced hooks[13]. Long lines can extend up to thirty miles long to maximize the number of fish caught[14]. These lines are baited with live fish, and then reeled in after a day to collect the catch.

Additional Fishing Methods[edit | edit source]

There are many additional commercial fishing methods which are less notable due to lower rates of utilization or smaller environmental impact. One such method is Dredging which is similar to bottom trawling, with the exception that a metal rake is used rather than a net in order to collect shellfish[13]. Midwater or Pelagic Trawling is similar to bottom trawling, but the net is dragged through water not along the bottom[14]. Methods such as Lobster and Crab Pots are also used to catch said species.

Ecological Implications[edit | edit source]

Multiple cumulative anthropogenic stressors to marine animal classes

Many marine species are facing multiple stressors with cumulative impacts. As direct exploitation of fish populations and bycatch of marine mammals, seabirds, and others continues to increase, the risk of severe biodiversity loss and extinction is increasing.

Benthic Habitat Loss[edit | edit source]

Benthic habitat loss is perhaps the most pronounced and obvious form of marine habitat modification. Typically, benthic habitats suffer damage from the use of invasive fishing procedures like bottom trawling. In recent years, roughly 1.3% of the ocean's seafloor surface was trawled every year[16]. This equates to an area around half the land area of the United States. Benthic ecosystem disruption and loss of life from commercial fishing methods may not be considered bycatch despite the immediate causal connection and vast damage.

Extinction Risk and Biodiversity Loss[edit | edit source]

Seabirds congregating around longlines

Our oceans are biodiversity hotspots. Biological and ecological processes in the marine environment also support life on land and maintain the biosphere. While the number of terrestrial species considered to be at risk of extinction is much larger than that of marine or anadromous species, declines in marine life are widespread and detrimental. Everything from top-level predators (e.g. cetaceans, sharks/rays, etc.) to the most fundamental component of marine food chains/ecosystems (phytoplankton) have experienced unprecedented declines from anthropogenic stressors[2][17].


Bycatch and the consequences of biodiversity loss extends far beyond the submerged world. Seabirds have been known to get entangled in fishing gear - especially longlines.

Greenhouse Gas Emissions[edit | edit source]

Trawling has the largest associated greenhouse gas emissions of any commercial fishing method. Through the disturbance of the sediments settled on the seafloor, trawling releases massive quantities of naturally sequestered carbon back into the atmosphere, worsening global warming and ocean acidification. The 1.47 billion tonnes of carbon dioxide released from trawling sediment disturbance is greater than the aviation sector, respectively.[16]

Participants[edit | edit source]

There are numerous participants involved in the acts of commercial fishing, both in regards to supporting and discouraging the acts.

Fisheries / Fish Trade Organizations[edit | edit source]

Fisheries and fish trade organizations are primarily focused on gaining profits by utilizing effective commercial fishing methods. For example, In the Japanese town of Taiji, dolphin hunting is a common and controversial practice that has been a subject of criticism and debate[18]. The captured dolphins are sold to aquariums or have their meat sold, sometimes fisherman kill dolphins in order to eliminate competition for the fish in the region[18]. This tactic is another byproduct from the effects of overfishing. These fisheries usually use methods like bottom trawling to maximize the catch of fish regardless of its consequences[13].

Seafood / Aquaculture Companies[edit | edit source]

Seafood and aquaculture companies typically benefit from the sale of seafood with there being controversy surrounding the means by which they do so. This can be seen through organizations such as the National Oceanic and Atmospheric Association (NOAA) and seafood companies such as StarKist. Products like tuna are sold with "dolphin-safe" checks which are administered by organizations like NOAA that are supposed to assure consumers that dolphins were not harmed in the fishing for the product[19]. However, this can be misleading as while some fisheries are monitored by third parties to assure that they are not harming dolphins, some fisheries can get verified through self declaration[19]. Companies can use unsustainable fishing methods and still be granted a dolphin-safe tag, bycatch of other species are also often not accounted for. Greenpeace, a non-profit activist group, put StarKist in last place in a group of 20 tuna brands that were ranked by how ethical and sustainable they were[20]. StarKist was given this rating due to the lack of transparency of fishing methods, and their association with destructive fisheries.

Governments[edit | edit source]

Governments can also be involved by allowing for underhanded business practices to happen without consequence. One notorious example of this is the violation of human rights of workers in Thai fisheries. Forced labor is a common occurrence with workers being subject to unfair treatment such as abuse and fraudulent deductions of workers' salaries[21]. In 2015, the Thai government claimed that in an investigation of 474,334 fishery workers, not a single case of forced labor was identified which is contrary to reports made by current and former fisher workers[21].

Advocacy Groups[edit | edit source]

There are numerous advocacy groups giving their take on how to tackle the issue of overfishing and its ecological implications. Groups like Oceana are strong on advocating for laws to promote sustainable fishing[22]. The idea of sustainable fishing has also seen criticism due to proposals of the idea lacking solid and constructive plans and for difficult implementations[23]. Other groups such as World Day for the End of Fishing (WoDEF) advocate for the complete halt of fishing and the removal of aquaculture farms[24]. Sea Shepherd, a conservation activism organization, is know for getting directly involved by physically intervening with illegal fishers by taking down ships[25].

Conclusion[edit | edit source]

The Commercial Fishing industry provides a good example of the challenges that arise from the presence of conflicting priorities and limitations between different groups. On the one hand there are the commercial fisheries who are trying to turn a profit and supply fish to meet the dietary demands of society. On the other hand are the ecosystems which are damaged and destroyed and the aquatic species which experience irreversible harm from the methods utilized by the fisheries.

Another observation which arises from the issues related to commercial fishing is the impact of technology and its role in society. In this case, as in innumerable others, the technologies in and of themselves are brilliant and achieve their goal of maximizing the number of fish caught. However, there are significant negative side effects of the technology to the environment and fish populations which must be considered.

An area which must be further analyzed is how these fishing methods and the priorities of the commercial fisheries can be balanced with the limitations and needs of the environment and in particular the oceanic ecosystems.

References[edit | edit source]


  1. ↑ Jackson, J. B. C. (2010). The future of the oceans past. Philosophical Transactions of the Royal Society B: Biological Sciences, 365(1558), 3765–3778. https://doi.org/10.1098/rstb.2010.0278
  2. ↑ a b Lotze, H. K., & Worm, B. (2009). Historical baselines for large marine animals. Trends in Ecology & Evolution, 24(5), 254–262. https://doi.org/10.1016/j.tree.2008.12.004
  3. ↑ Pusceddu, A., Bianchelli, S., Martín, J., Puig, P., Palanques, A., Masqué, P., & Danovaro, R. (2014). Chronic and intensive bottom trawling impairs deep-sea biodiversity and ecosystem functioning. Proceedings of the National Academy of Sciences, 111(24), 8861–8866. https://doi.org/10.1073/pnas.1405454111
  4. ↑ Hiddink, J. G., Jennings, S., Sciberras, M., Szostek, C. L., Hughes, K. M., Ellis, N., Rijnsdorp, A. D., McConnaughey, R. A., Mazor, T., Hilborn, R., Collie, J. S., Pitcher, C. R., Amoroso, R. O., Parma, A. M., Suuronen, P., & Kaiser, M. J. (2017). Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance. Proceedings of the National Academy of Sciences, 114(31), 8301–8306. https://doi.org/10.1073/pnas.1618858114
  5. ↑ a b Hsu, J. (2009, May 25). Overfishing goes back centuries, log books reveal. LiveScience. https://www.livescience.com/5445-overfishing-centuries-log-books-reveal.html.
  6. ↑ a b Overfishing. National Geographic. (2010, April 27). https://www.nationalgeographic.com/environment/article/critical-issues-overfishing.
  7. ↑ More than a third of fish stocks are being overfished, FAO warns.(2020, June 8). Al Jazeera. https://www.aljazeera.com/economy/2020/6/8/more-than-a-third-of-fish-stocks-are-being-overfished-fao-warns.
  8. ↑ What is a Fisheries Subsidy? Food and Agriculture Organization. (n.d.). https://www.fao.org/3/y4446e/y4446e0k.htm.
  9. ↑ a b Subsidies and Fisheries. Food and Agriculture Organization. (n.d.). https://www.fao.org/3/y4647e/y4647e06.htm.
  10. ↑ Fisheries subsidies: A critical issue for trade and Sustainable Development at the WTO. UNEP. (2008, May). https://wedocs.unep.org/bitstream/handle/20.500.11822/23020/Fisheries_Subsidies_Intro.pdf?sequence=1&isAllowed=y.
  11. ↑ a b The Last Wild Hunt: Deep-sea Fisheries Scrape Bottom of the Sea. Marine Conservation. (2007, February 17). https://marine-conservation.org/archive/mcbi/LastWildHuntPR_FinalFeb14_2007.pdf?ID=150.
  12. ↑ University of Western Australia. (2021, October 29). Scientists join International Push to ban harmful fisheries subsidies. Phys.org. https://phys.org/news/2021-10-scientists-international-fisheries-subsidies.html.
  13. ↑ a b c d e f Sustainable Fisheries. (n.d.). Commercial Fishing Methods. https://sustainablefisheries-uw.org/seafood-101/commercial-fishing-methods/
  14. ↑ a b c d e British Sea Fishing.co.uk. (n.d.). Commercial Fishing Methods. https://britishseafishing.co.uk/commercial-fishing-methods/
  15. ↑ Best Fish Forward. (2020, June 10). An Introduction to Fishing Methods. https://www.bestfishforward.com/fish-tales/2020/5/1/fishing-methods.
  16. ↑ a b Sala, E., Mayorga, J., Bradley, D., Cabral, R. B., Atwood, T. B., Auber, A., Cheung, W., Costello, C., Ferretti, F., Friedlander, A. M., Gaines, S. D., Garilao, C., Goodell, W., Halpern, B. S., Hinson, A., Kaschner, K., Kesner-Reyes, K., Leprieur, F., McGowan, J., … Lubchenco, J. (2021). Protecting the global ocean for biodiversity, food and climate. Nature, 592(7854), 397–402. https://doi.org/10.1038/s41586-021-03371-z
  17. ↑ Boyce, D. G., Lewis, M. R., & Worm, B. (2010). Global phytoplankton decline over the past century. Nature, 466(7306), 591–596. https://doi.org/10.1038/nature09268
  18. ↑ a b McNeill, D. (2007, January 2). Taiji: Japan's Dolphin Cull and the Clash of Cultures. The Asia-Pacific Journal. https://apjjf.org/-David-McNeill/2306/article.html.
  19. ↑ a b Watson, W. (2015, April 29). 'Dolphin Safe' labels on canned tuna are a fraud. Forbes. https://www.forbes.com/sites/realspin/2015/04/29/dolphin-safe-labels-on-canned-tuna-are-a-fraud/?sh=5e916cfd295e.
  20. ↑ Top 20 Tuna Brands ranked. Greenpeace. (2017). https://www.greenpeace.org/usa/oceans/tuna-guide/.
  21. ↑ a b Hidden Chains: Rights Abuses and Forced Labor in Thailand’s Fishing Industry. Human Rights Watch. (2018, January 13). https://www.hrw.org/report/2018/01/23/hidden-chains/rights-abuses-and-forced-labor-thailands-fishing-industry#.
  22. ↑ 5 steps towards sustainable fishing. Oceana. (2009, September). https://oceana.org/reports/5-steps-towards-sustainable-fishing/.
  23. ↑ Stafford, Richard(2019, January 1). Sustainability: A flawed concept for fisheries management?. Elementa: Science of the Anthropocene. doi: https://doi.org/10.1525/elementa.346
  24. ↑ End of fishing. World day for the End of Fishing. (2021, March 26). https://www.end-of-fishing.org/en/.
  25. ↑ Enders, C. (2015, June 5). Can sea shepherd survive its own success? The Guardian. https://www.theguardian.com/environment/2015/jun/05/sea-shepherd-whale-wars-animal-planet.
Retrieved from "https://en.wikibooks.org/w/index.php?title=Lentis/Ecological_Implications_of_Commercial_Marine_Fishing&oldid=4191414"